Thrust bearing assembly

ABSTRACT

A thrust bearing assembly in which each thrust pad is individually mounted on a deflection element. An embodiment of the invention comprises a rotating bearing runner having a wear resistant face and a stationary bearing carrier defining a plurality of cavities disposed annularly around the carrier. A deflection element, such as a Belleville washer, is disposed in a cavity of the plurality of cavities and a pad is disposed over the deflection element. The pad is at least partially disposed within the cavity. The wear resistant face of the rotating bearing runner contacts the pad.

BACKGROUND

1. Field of the Invention

The present invention relates to thrust bearing assemblies, and moreparticularly to a hydrodynamic thrust bearing assembly having thrustpads individually mounted on resilient deflection elements, such asBelleville washers.

2. Background of the Invention

Most conventional downhole drilling motors use rolling element-typebearings, such as ball rollers or angular contact rollers. U.S. Pat. No.5,074,681 to Turner et al. discloses an example of ball rollers. U.S.Pat. No. 5,248,204 to Livingston et al. discloses an example of angularcontact rollers. Typically, these rolling element-type bearings arelubricated by the drilling fluid (mud) or by clean oil when encased in asealed oil chamber. Due to the high loads, pressure, and abrasiveconditions, bearing life is typically only several hundred hours.

Motors typically have a multiple number of bearings. The bearings can beresiliently supported on Belleville washers to equalize loading amongbearings and to absorb shock. Rolling element-type bearings are nottolerant of abrasives and thus wear quickly when exposed to mudlubrication. Once wear occurs, loads between the individual balls becomeuneven and wear rates accelerate. Indeed, rolling element balls takenfrom failed units are sometimes half their original diameter. For theoil-lubricated bearings, once the seals fail, wear occurs in a similarway.

Another type of bearing used in downhole drilling motors is ahydrodynamic or sliding surface type. U.S. Pat. No. 4,560,014 to Geczydiscloses an example of this hydrodynamic bearing type, which usesrigidly mounted pads manufactured of industrial diamond. The diamondpads are mud-lubricated and slide against each other. These bearings,however, are extremely expensive and only marginally increase servicelife.

Other examples of hydrodynamic bearings are disclosed in the inventor'sprevious U.S. Pat. Nos. 5,441,347 to Ide and U.S. Pat. No. 5,620,260also to Ide, both of which are incorporated herein by reference. Thesepad type hydrodynamic thrust bearings include a carrier and a pluralityof bearing pads circumferentially spaced about the carrier. The pads maybe provided with individual support structures and supported in thecarrier, or may be integrally formed with the carrier.

SUMMARY OF THE INVENTION

An embodiment of the present invention provides a hydrodynamic thrustbearing assembly in which each thrust pad is individually mounted on adeflection element. Rather than mounting an entire bearing having fixedpads on a resilient member (e.g., spring), the present inventionresiliently mounts the individual thrust pads, thereby avoiding costlyfinish-grinding/lapping of the complete bearing assembly.

An exemplary thrust bearing assembly according to an embodiment of thepresent invention comprises a rotating bearing runner having a wearresistant face and a stationary bearing carrier defining a plurality ofcavities disposed annularly around the carrier. A deflection element isdisposed in a cavity of the plurality of cavities and a pad is disposedover the deflection element. The pad is at least partially disposedwithin the cavity. The wear resistant face of the rotating bearingrunner contacts the pad.

Another embodiment of the present invention provides a thrust bearingassembly for a downhole motor comprising a first stationary bearingcarrier defining a first plurality of cavities disposed annularly aroundthe first stationary bearing carrier, a second stationary bearingcarrier defining a second plurality of cavities disposed annularlyaround the second stationary bearing carrier, and a rotating bearingrunner disposed between the first stationary bearing carrier and thesecond stationary bearing carrier. The rotating bearing carrier has afirst wear resistant face and a second wear resistant face. Each cavityof the first plurality of cavities and the second plurality of cavitiesholds a deflection element and a pad disposed over the deflectionelement. The first wear resistant face is in contact with the pads ofthe first stationary bearing carrier. The second wear resistant face isin contact with the pads of the second stationary bearing carrier.

Another embodiment of the present invention provides a downhole drillingapparatus that includes a progressive cavity drive train. The apparatuscomprises a housing structure, a stator, a rotor, and a thrust bearingassembly. The stator has a longitudinal axis. The rotor has a truecenter and is located within the stator. The stator and the rotor eachhave coacting helical lobes that are in contact with one another at anytransverse section. The stator has one more helical lobe than the rotorsuch that a plurality of progressive cavities is defined between therotor and the stator. The rotor is adapted to rotate within the statorsuch that the true center of the rotor orbits the axis of the stator.The orbit has a predetermined radius and the orbiting motion of therotor causes a progression of the progressive cavities in the directionof the axis of the stator. The thrust bearing assembly is coupled to therotor and comprises a rotating bearing runner having a wear resistantface and a stationary bearing carrier defining a plurality of cavitiesdisposed annularly around the carrier. A deflection element is disposedin a cavity of the plurality of cavities and a pad is disposed over thedeflection element. The pad is at least partially disposed within thecavity. The wear resistant face of the rotating bearing runner contactsthe pad.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevation view partly in section of the overall structureof a downhole drilling apparatus according to an embodiment of thepresent invention.

FIG. 2A is a sectional view of an exemplary thrust bearing assemblyinstalled in a downhole motor, according to an embodiment of the presentinvention.

FIG. 2B is an enlarged view of a portion of the thrust bearing assemblyof FIG. 2A.

FIG. 2C is a sectional view of the thrust bearing assembly of FIG. 2Aprior to welding.

FIG. 3A is a plan view of an exemplary bearing carrier, according to anembodiment of the present invention.

FIG. 3B is a sectional view of the bearing carrier of FIG. 3A along lineA-A.

FIG. 3C is an isometric view of a section of the bearing carrier of FIG.3A along line A-A.

FIG. 4A is a plan view of an exemplary runner, according to anembodiment of the present invention.

FIG. 4B is a sectional view of the runner of FIG. 4A along line A-A.

FIG. 4C an isometric view of a section of the runner of FIG. 4A alongline A-A.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of thrust bearing assemblies are described in this detaileddescription of the invention. In this detailed description, for purposesof explanation, numerous specific details are set forth to provide athorough understanding of embodiments of the present invention. Oneskilled in the art will appreciate, however, that embodiments of thepresent invention may be practiced without these specific details. Inother instances, structures and devices are shown in block diagram form.Furthermore, one skilled in the art can readily appreciate that thespecific sequences in which methods are presented and performed areillustrative and it is contemplated that the sequences can be varied andstill remain within the spirit and scope of embodiments of the presentinvention.

An embodiment of the present invention provides a novel, longer life,higher capacity, lower cost hydrodynamic bearing that operates in, forexample, a mud-lubricated or sealed oil bath-lubricated drilling motorbearing system. The pad wear surface can be made of a material that isharder than the particles typically found in the mud and that does notwear when maximum loads are kept in approximately the 1000 to 2000 psirange. Examples of suitable pad wear material include silicon carbideand tungsten carbide. Load equalization among individual pads withineach bearing can be accomplished by resiliently mounting each thrust padon deflection elements, such as Belleville washers. This resilientmounting differs from mounting the entire bearing, encompassing fixedpads, on a resilient element (spring), as has been done in the priorart. Indeed, resiliently mounting individual pads eliminates costlyfinish-grinding/lapping of the complete bearing assembly.

When designed to fit into existing motor bearing envelopes, thrustloading of approximately 1000 psi or less can be achieved. Testsconducted in mud lubrication at these loads have shown virtually nowear. In a preferred embodiment, the present invention includes a numberof rotating disc members of abrasion-resistant hard wear surfaces and anumber of stationary pad-type bearing members opposite one or both sidesof the rotating member. The bearing members comprise pad carriers with aplurality of cavities for fitting hard ceramic wear pads on resilientelements, such as Belleville washers.

In an embodiment of a method for manufacturing a thrust bearingaccording to the present invention, the components are first looselyassembled. The stationary bearing carriers are then bolted or weldedtogether after assembly with a preload (e.g., a slight compression) onthe springs. This construction ensures that all components are held inposition for proper alignment. Because of the difficulty in predictingprecise loads downhole, the present invention can be designed with anoverload protection blank runner that engages prior to bottoming of theBelleville washers. For example, a blank runner can be coupled to abearing carrier of the thrust bearing assembly and configured to engagea blank overload stop. As used herein, the term “coupled” encompasses adirect connection, an indirect connection, or a combination thereof.

Illustrating one particular application of the present invention, FIG. 1shows the overall structure of a progressive cavity drilling apparatusin which a hydrodynamic pad type thrust bearing of the present inventioncan be used. As shown, the apparatus includes a drill string 15, aprogressive cavity drive train, a drill bit drive shaft 16, and a drillbit 26. The drive train includes a progressive cavity device and acoupling for converting the motion of the rotor of the progressivecavity device, e.g., orbiting of the rotor and the rotational motion ofthe rotor, into rotation about a single axis at the same speed. Thiscoupling, which is contained in the lower part of housing 10 and is notvisible in FIG. 1, is a joint assembly including one or more thrustbearing members of the present invention. The joint assembly can be, forexample, either a mud-lubricated or sealed oil bath-lubricated drillingmotor bearing system.

As illustrated in FIG. 1, the progressive cavity device A has a stator,a rotor, a passageway 11 for fluid to enter between the stator and therotor, and a passageway 20 for the fluid to exit therefrom. In thedrawings, the housing 10 and its flexible lining 14 are held againstmovement so that they function as the stator in the device A and theshaft 12 functions as the rotor. The housing 10 is tubular and itsinterior communicates with inlet 11 in the top portion of the lining 14to provide a passageway for fluid to enter the progressive cavity deviceA. Outlet 20 in the bottom portion of the lining 19 serves as thepassageway for fluid to discharge from the progressive cavity device A.The shaft 12 is precisely controlled so as to roll within the lining 14.The progressive cavity device A is attached to the lower end of a drillstring 15.

The lower end of the rotor shaft 12 includes a shaft connection 18 a.The shaft connection allows the rotor 12 to be directed to a stub shaftof the coupling. One end of the coupling is directly connected, bythreading, splining, or the like, to the rotor shaft 12. The other endof the coupling is similarly connected to a drill bit drive shaft 16.Typically, the coupling includes separate stub shafts that are connectedto the rotor shaft 12 and drive shaft 16 by connecting means such asthreads, splines, and the like. Of course, a stub shaft could beintegrally formed (connected) to either of these shafts, if desired. Thedrill bit drive shaft 16 is rotatably connected to a conventional drillbit 26.

The progressive cavity train functions as a fluid motor or drivingapparatus for driving the drilling apparatus shown in FIG. 1. Thus, apressurized fluid, typically water carrying suspended particles commonlyreferred to as “mud,” is forced into the progressive cavity device. Therotor 12 responds to the flowing fluid to produce a rotor driving motionthat is simultaneously a rotation, an oscillation, and an orbit. Thecoupling attached to the rotor 12 at connection point 18 a and alignedwith the true center 28 of the rotor described above converts this rotordriving motion into rotational driving motion substantially about asingle axis.

FIGS. 2A and 2B show sectional views of an exemplary thrust bearingassembly 150 installed in a downhole motor, according to an embodimentof the present invention. As shown, a drill motor shaft 104 is coupledto a drill bit (not shown) located below the thrust bearing assembly150. Drill motor shaft 104 is housed in drill casings 102 and 103.Stationary bearing members 110 and 101 are fixed between the drillcasings 102 and 103. Stationary bearing members 110 are bearingcarriers. Stationary bearing member 101 is a blank overload stop.Bearing carriers 110 and blank overload stop 101 are fixed in the drillstring assembly via compressive forces on the top and bottom applied bydrill casings 102 and 103.

Rotating bearing runners 106 are locked to the rotating shaft 104 withcompressive forces on the top and bottom by the threaded drill casingmember 105. Wear resistant inserts 111 (e.g., made of silicon carbideand tungsten carbide) are fitted to rotating bearing runners 106 withadhesive. Optionally, wear resistant inserts 111 can be omitted ifrotating bearing runners 106 have integral wear resistant faces. Forexample, bearing runners 106 can be entirely made from a wear resistantmaterial, such as silicon carbide and tungsten carbide.

Each stationary bearing carrier 110 includes one or more thrust pads.Each thrust pad can be resiliently mounted within an individual cavity.In one embodiment shown in FIG. 3A and discussed below, the individualthrust pads are disposed annularly around a carrier. As shown in thecross-sectional view of FIG. 2B, a pad 109 can be resiliently mounted ona deflection element 107 within a counterbore 115 of bearing carrier110. In this case, pad 109 is a hard ceramic disc and deflection element107 is a resilient washer, such as a Belleville washer. A steel disc 108can optionally be provided between the pad 109 and deflection element107 to uniformly distribute the deflection element loads to the bottomof the pad 109 to eliminate any stress risers.

As shown in FIG. 2A, to provide overload protection, an exemplary thrustbearing assembly of the present invention can include a blank steelrunner 100 that engages the blank overload stop 101 just prior tobottoming of the deflection elements 107.

As shown in FIG. 2B, welds 152 at the base of each bearing carrier 110lock the entire assembly together and hold the individual components inposition. FIG. 2C illustrates a sectional view of bearing assembly 150prior to this welding, showing blank overload stop 101, blank steelrunner 100, stationary bearing carrier 110, rotating bearing runners106, and a pad 109 (e.g., a ceramic wear disc) assembled together.

FIGS. 3A-3C illustrate an exemplary bearing carrier 110 for use in athrust bearing assembly of an embodiment of the present invention. Asshown in FIGS. 3A and 3C, bearing carrier 110 includes a bearing carrierhousing having two groups of cavities annularly disposed around thecarrier. The first group faces in one direction generally along the axisof the carrier 110, and the second group faces in generally the oppositedirection along the axis. A deflection element 107 is disposed in eachcavity. A pad 109 (e.g., a wear resistant insert) is disposed over eachdeflection element 107. Optionally, a load distribution washer 108 isdisposed between the deflection element 107 and the pad 109. Deflectionelement 107 is a resilient washer, such as a Belleville washer. Loaddistribution washer 108 is a steel disc, for example. Pad 109 is, forexample, an abrasion resistant circular pad as shown. In one embodiment,deflection element 107, load distribution washer 108, and pad 109 areloosely assembled within cavity 115, are held in place by the confinesof cavity 115 and by bearing runner 106 (specifically, insert 111, ifprovided), and are not attached to each other.

In an aspect of the present invention, as shown in FIGS. 2B, 3B, and 3C,pad 109 is at least partially disposed within cavity 115. In thismanner, pad 109 is constrained radially within cavity 115, but is stillfree to move axially as deflection element 107 compresses and expands.Thus, each pad 109 can float axially within its cavity 115 as bearingrunner 106 rotates and contacts pads 109. Such independent axialmovement provides load equalization among the individual pads within thebearing carrier 110.

FIGS. 4A-4C illustrate an exemplary bearing runner 106 for use in athrust bearing assembly of an embodiment of the present invention.Bearing runner 106 rotates with the drill motor shaft. As shown best inFIG. 4B, bearing runner 106 includes a bearing runner housing with wearresistant, or abrasion resistant, rings 111 that are fitted to therunner, for example, by adhesive. Optionally, rings 111 can be omittedif bearing runner 106 has integral wear resistant faces.

Although embodiments of the present invention have been described in thecontext of downhole drilling motors, one of ordinary skill in the artwould appreciate that the thrust bearing assemblies of the presentinvention are equally applicable to other applications for thrustbearings, such as in rock crushing equipment. Therefore, notwithstandingthe particular benefits associated with applying the present inventionto drilling motors, the present invention should be considered broadlyapplicable to any application in need of thrust bearings.

The foregoing disclosure of the preferred embodiments of the presentinvention has been presented for purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Many variations andmodifications of the embodiments described herein will be apparent toone of ordinary skill in the art in light of the above disclosure. Thescope of the invention is to be defined only by the claims appendedhereto, and by their equivalents.

Further, in describing representative embodiments of the presentinvention, the specification may have presented the method and/orprocess of the present invention as a particular sequence of steps.However, to the extent that the method or process does not rely on theparticular order of steps set forth herein, the method or process shouldnot be limited to the particular sequence of steps described. As one ofordinary skill in the art would appreciate, other sequences of steps maybe possible. Therefore, the particular order of the steps set forth inthe specification should not be construed as limitations on the claims.In addition, the claims directed to the method and/or process of thepresent invention should not be limited to the performance of theirsteps in the order written, and one skilled in the art can readilyappreciate that the sequences may be varied and still remain within thespirit and scope of the present invention.

1. A thrust bearing assembly comprising: a rotating bearing runnerhaving a wear resistant face; a stationary bearing carrier defining aplurality of cavities disposed annularly around the carrier; adeflection element disposed in a cavity of the plurality of cavities;and a pad disposed over the deflection element, the pad at leastpartially disposed within the cavity, and the wear resistant face of therotating bearing runner contacting the pad.
 2. The thrust bearingassembly of claim 1, further comprising a load distribution washerdisposed between the deflection element and the pad.
 3. The thrustbearing assembly of claim 2, the load distribution washer comprising asteel disc.
 4. The thrust bearing assembly of claim 1, the pad and thecavity being generally circular, and the pad comprising a ceramic disc.5. The thrust bearing assembly of claim 1, the deflection elementcomprising a Belleville washer.
 6. The thrust bearing assembly of claim1, the cavity having a longitudinal axis, the cavity constraining thepad in a radial direction while allowing the pad to move in a directiongenerally along the longitudinal axis.
 7. The thrust bearing assembly ofclaim 1, the wear resistant face of the rotating bearing runnercomprising a wear resistant insert.
 8. The thrust bearing assembly ofclaim 1, the deflection element being partially compressed beforeoperation of the thrust bearing assembly.
 9. The thrust bearing assemblyof claim 1, the deflection element and the pad being unconnected.
 10. Athrust bearing assembly for a downhole motor comprising: a firststationary bearing carrier defining a first plurality of cavitiesdisposed annularly around the first stationary bearing carrier; a secondstationary bearing carrier defining a second plurality of cavitiesdisposed annularly around the second stationary bearing carrier; and arotating bearing runner disposed between the first stationary bearingcarrier and the second stationary bearing carrier, the rotating bearingcarrier having a first wear resistant face and a second wear resistantface, each cavity of the first plurality of cavities and the secondplurality of cavities holding a deflection element and a pad disposedover the deflection element, the first wear resistant face in contactwith the pads of the first stationary bearing carrier, and the secondwear resistant face in contact with the pads of the second stationarybearing carrier.
 11. The thrust bearing assembly of claim 10, furthercomprising a load distribution washer disposed between the deflectionelement and the pad of the each cavity.
 12. The thrust bearing assemblyof claim 11, the load distribution washer comprising a steel disc. 13.The thrust bearing assembly of claim 10, the first wear resistant faceand the second wear resistant face comprising abrasion resistant rings.14. The thrust bearing assembly of claim 10, the first stationarybearing carrier being fixed to the second stationary bearing carrier byone of bolting and welding.
 15. The thrust bearing assembly of claim 10,the pad comprising a ceramic disc.
 16. The thrust bearing assembly ofclaim 10, the deflection element comprising a Belleville washer.
 17. Thethrust bearing assembly of claim 10, the first stationary bearingcarrier further defining a third plurality of cavities facing in adirection opposite to the first plurality of cavities, each cavity ofthe third plurality of cavities holding a deflection element and a paddisposed over the deflection element, and the thrust bearing assemblyfurther comprising: a second rotating bearing runner having a first wearresistant face and a second wear resistant face, the first wearresistant face of the second rotating bearing runner in contact with thepads of the third plurality of cavities; and a stationary bearing memberdefining a fourth plurality of cavities, each cavity of the fourthplurality of cavities holding a deflection element and a pad disposedover the deflection element, the pads of the fourth plurality ofcavities in contact with the second wear resistant face of the secondbearing runner.
 18. The thrust bearing assembly of claim 17, thestationary bearing member adapted to be compressed by a drill casing.19. The thrust bearing assembly of claim 17, further comprising a blankrunner coupled to the second stationary bearing carrier, the blankrunner configured to engage a blank overload stop prior to bottoming ofthe deflection elements.
 20. The thrust bearing assembly of claim 10,each cavity of the first and second pluralities of cavities having alongitudinal axis, the each cavity constraining the pad in a radialdirection while allowing the pad to move in a direction generally alongthe longitudinal axis.
 21. The thrust bearing assembly of claim 10, eachcavity of the first and second pluralities of cavities comprising acounterbored circular hole.
 22. A downhole drilling apparatus thatincludes a progressive cavity drive train comprising: a housingstructure; a stator, the stator having a longitudinal axis; a rotorhaving a true center, the rotor being located within the stator; thestator and the rotor each having coacting helical lobes that are incontact with one another at any transverse section, the stator havingone more helical lobe than the rotor such that a plurality ofprogressive cavities is defined between the rotor and the stator, andthe rotor being adapted to rotate within the stator such that the truecenter of the rotor orbits the axis of the stator, the orbit having apredetermined radius and the orbiting motion of the rotor causing aprogression of the progressive cavities in the direction of the axis ofthe stator; a thrust bearing assembly coupled to the rotor, the thrustbearing assembly comprising a rotating bearing runner having a wearresistant face; a stationary bearing carrier defining a plurality ofcavities disposed annularly around the carrier; a deflection elementdisposed in a cavity of the plurality of cavities; and a pad disposedover the deflection element, the pad at least partially disposed withinthe cavity, and the wear resistant face of the rotating bearing runnercontacting the pad.
 23. The downhole drilling apparatus of claim 22, thecavity having a longitudinal axis, the cavity constraining the pad in aradial direction while allowing the pad to move in a direction generallyalong the longitudinal axis.